Support registration of custom preferences.

Custom global and request context preferences can now be registered via
CefBrowserProcessHandler::OnRegisterCustomPreferences. CefRequestContext
now extends CefPreferenceManager and global preferences can be accessed
via CefPreferenceManager::GetGlobalPreferenceManager.

libcef_dll/cpptoc/preference_registrar_cpptoc.h

@@ -0,0 +1,38 @@
+// Copyright (c) 2022 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+//
+// ---------------------------------------------------------------------------
+//
+// This file was generated by the CEF translator tool. If making changes by
+// hand only do so within the body of existing method and function
+// implementations. See the translator.README.txt file in the tools directory
+// for more information.
+//
+// $hash=79809d65530b8405f3fed4adf7c55f8d28f515e0$
+//
+
+#ifndef CEF_LIBCEF_DLL_CPPTOC_PREFERENCE_REGISTRAR_CPPTOC_H_
+#define CEF_LIBCEF_DLL_CPPTOC_PREFERENCE_REGISTRAR_CPPTOC_H_
+#pragma once
+
+#if !defined(BUILDING_CEF_SHARED)
+#error This file can be included DLL-side only
+#endif
+
+#include "include/capi/cef_preference_capi.h"
+#include "include/cef_preference.h"
+#include "libcef_dll/cpptoc/cpptoc_scoped.h"
+
+// Wrap a C++ class with a C structure.
+// This class may be instantiated and accessed DLL-side only.
+class CefPreferenceRegistrarCppToC
+    : public CefCppToCScoped<CefPreferenceRegistrarCppToC,
+                             CefPreferenceRegistrar,
+                             cef_preference_registrar_t> {
+ public:
+  CefPreferenceRegistrarCppToC();
+  virtual ~CefPreferenceRegistrarCppToC();
+};
+
+#endif  // CEF_LIBCEF_DLL_CPPTOC_PREFERENCE_REGISTRAR_CPPTOC_H_